EP3565656A1

EP3565656A1 - Method for producing d-allulose crystals

Info

Publication number: EP3565656A1
Application number: EP18700791.9A
Authority: EP
Inventors: Baptiste Boit; Geoffrey LACROIX; Laurent Rossi
Original assignee: Roquette Freres SA
Current assignee: Roquette Freres SA
Priority date: 2017-01-05
Filing date: 2018-01-05
Publication date: 2019-11-13
Also published as: JP2023011728A; US11945835B2; US20190330253A1; FR3061413B1; WO2018127668A1; US20240343751A1; FR3061413A1; MX2019008062A; JP2020514294A; KR20190098991A

Abstract

The invention relates to a new method for producing D-allulose crystals that allows for a continuous production process and ensures a high yield. The invention also relates to new D-allulose crystals. The invention further relates to the use of a nanofiltration unit in a method for producing D-allulose crystals to improve the yield and/or quality of the resulting crystals.

Description

Process for manufacturing D-allulose crystals

Field of the invention

The invention relates to a new process for the manufacture of D-allulose crystals which makes it possible to work continuously and to obtain a high yield. The invention also relates to new D-allulose crystals. Another subject of the invention relates to the use of a nanofiltration unit in a process for producing D-allulose crystals in order to improve the yield and / or the quality of the crystals obtained. Prior art

D-allulose (or D-psicose) is a rare sugar with a sweetness equal to 70% of that of sucrose. Unlike the latter, D-allulose does not cause weight gain because it is not metabolized by humans. It has a very low caloric value (0.2 kcal per gram) and thus prevents fat gain. In addition, studies have shown that D-allulose is non-cariogenic or even anti-cariogenic. Thus, these properties have recently generated a very important interest in the food and pharmaceutical industries.

Although it is possible to obtain D-allulose chemically, for example by reacting an aqueous solution of glucose in an acid medium in the presence of an ammonium molybdate catalyst, D-allulose is generally obtained. enzymatically, by reacting an aqueous solution of D-fructose with a D-psicose epimerase as described for example in the application WO2015 / 032761 A1 in the name of the Applicant. In both cases, the reaction is not complete. For example, the amount of D-fructose converted to D-allulose after epimerization is generally less than 30%.

Thus, at the end of the epimerization reaction, it is necessary to carry out a step of separation of D-allulose, to increase the richness of the resulting D-allulose composition. In order to achieve this separation, chromatography of the composition resulting from the epimerization reaction is carried out very generally, for example by continuous chromatography of simulated moving bed type.

JP2001354690 A discloses a method of manufacturing a D-allulose syrup starting from a mixture of fructose and D-allulose, said process comprising a separation step consisting of a continuous chromatography step using a particular sequence of samples of the different products of the mixture. A fraction rich in D-allulose (whose richness in D-allulose can reach 98%) and a fraction rich in fructose are recovered. The recovery yield in the D-allulose rich fraction is 96%.

At the end of the separation steps mentioned above, liquid compositions rich in D-allulose are obtained. Thus, these liquid compositions, generally called syrups, are used for the manufacture of food or pharmaceutical products.

By way of example, the application WO 2015/094342 also in the name of the Applicant describes the manufacture of solid food products comprising a syrup of D-allulose, comprising from 50 to 98% of D-allulose and a native protein. It is mainly in this form of syrup that various companies have announced the marketing of D-allulose to date.

D-Allulose is also marketed in the form of powders. However, as explained below, their fabrications can be quite complex.

It is possible to produce powders using, for example, atomization techniques. However, the atomized powders, the composition of which depends on the atomized raw material, generally comprise large amounts of impurities. Moreover, these atomized powders are weakly crystalline; they are very hygroscopic and this causes problems with water resistance. This also creates generally larger caking phenomena.

Because of these difficulties, the atomization of D-allulose has been poorly described in the literature. By way of example, mention may be made of EP1860195 which describes the atomization of a mixture comprising D-allulose and D-allose. With regard to the enantiomer of D-allulose, L-allulose, mention may be made of JP 4761424 which describes the atomization of a cooked mass of L-allulose.

It is also possible to produce powders by granulation techniques, as described for example in the application WO2016 / 012853 in the name of the Applicant.

Another form of powders relates to crystals obtained by crystallization of a stock solution of D-allulose.

A process for producing D-allulose crystals has been described in document CN 104447888 A. This document describes more particularly in the examples a process comprising a step of manufacturing a solution of D-allulose from glucose using a molybdate catalyst and then a decolorization step of this solution using activated charcoal and filtration to remove the activated carbon, an electrodialysis deionization step, a separation step by continuous chromatography to form a solution D-allulose having a purity ranging from 70 to 90%, a step of concentration of said solution to obtain a concentrated solution of D-allulose, followed by a crystallization step in ethanol to obtain a crystalline product of D-allulose, allulose of limited purity, at most 99%. No crystallization yield is indicated in this document.

Another method of crystallization has also been described in WO 201 1/1 19004 in the name of CJ Cheiljedang in which the crystallization yield is of the order of 50%. This process for manufacturing D-allulose crystals comprises a step of providing a solution of D-allulose, a step of purifying this solution, a step of concentrating the D-allulose solution to provide a stock solution and a solution of D-allulose. step of crystallization of this mother solution, wherein the crystallization step is carried out by maintaining the stock solution in its metastable zone. The purification step described in this document is a chromatography separation step, which makes it possible to separate the D-allulose from the fructose. This document recognizes, however, that the manufacture of powders in the form of crystals is difficult to implement:

· Firstly, this crystallization is difficult to control as described in [36], in which it is stated that the crystallization must be carried out carefully, by continuous observation of the crystals, also measuring the concentration of the supernatant in order to adjust the temperature in the crystallizer. However, this document is silent on why it is difficult to achieve this crystallization.

In addition, the crystals obtained have a size of less than 200 μηη (see paragraph

[89]) and are therefore, because of their small size, difficult to separate from the mother waters of crystallization during centrifugation. The recovered crystals are also difficult to handle during later use.

WO 2016/064087, also in the name of CJ Cheiljedang, also describes in Example 3 a process for manufacturing D-allulose crystals in which a stock solution is introduced into a crystallizer at four distinct times. Between each introduction, four cycles of heating and cooling are carried out, which leads to a process that lasts more than 80 hours. In comparison with the method described in WO 201 1/1 19004, the crystallization yield is not improved (it is 52.8%). The crystals obtained have a larger average size (mean aperture equal to 374 μηη). However, the crystals obtained have impurities. Moreover, the crystals that are marketed by the company CJ Cheiljedang have a needle shape, which leads to a flow that is not completely satisfactory.

It appears from the foregoing that many problems still remain in the manufacture of D-allulose crystals.

First, the overall yield of D-allulose crystals is excessively low. By "overall yield of D-allulose crystals" is meant the ratio, expressed as dry mass, of the mass of D-allulose crystals obtained on the mass of D-fructose introduced. This low yield, of the order of 15% relative to D-fructose, is essentially related to the yields of epimerization (less than 30%) and crystallization (generally of the order of 50%).

In order to improve the efficiency of the processes, it is therefore imperative to carry out "recycling steps". By "recycling step" in a process is meant the reuse in a previous step of the process of a product fraction obtained in a separation step. By "separation step" in the present Application is meant any step for separating a composition comprising a product A and a product B in at least a first fraction richer in product A and a second fraction richer in product B. The fraction may be in any form, for example in solid form, in liquid form, or even in the form of a solid suspension in a liquid. A separation step can be of any type, for example a chromatography step, in which the liquid composition is separated into at least two liquid fractions, or else a crystallization step where a liquid composition is separated into a solid fraction and a fraction. liquid.

Steps for recycling high fructose fractions have already been described in order to improve the yield of the process for manufacturing D-allulose syrups. In particular, the document JP2001354690 A previously mentioned describes the recycling of the fructose-rich fraction obtained during the chromatography step to subject it to the epimerization step. This makes it possible to improve the yield of D-allulose in the form of a liquid composition.

It is by seeking to apply the teachings of this document in a process for manufacturing D-allulose crystals (such as, for example, that described in document WO 201 1/1 19004) that the Applicant has found that these were not simply transposable.

Indeed, when recycling the high fructose fraction (see FIG. 1), the Applicant has found that the mother solution obtained becomes increasingly difficult to crystallize. After a while, this crystallization becomes impossible even as demonstrated in the Examples section.

On the other hand, still with the aim of improving the overall yield of D-allulose crystals of the process, the Applicant has also attempted to carry out a recycling of the mother liquors of crystallization (that is to say of the solution rich in D-allulose which is obtained after separation of the crystals obtained during the crystallization step) by mixing them with a composition of D-allulose to form, after concentration, a new stock solution (see FIG. 2). It was able to observe (see the Examples section) that this recycling of mother liquors caused the same difficulties, and this even more rapidly than in the case of the recycling of the high-fructose fraction.

In these two cases described above, stops in the production of D-allulose crystals must therefore be made.

Moreover, the Applicant has found that, even without carrying out recycling, by transposing the teachings described above into a continuous industrial process for manufacturing D-allulose crystals, "instabilities" are observed. These instabilities result in mass-cooked crystals inexplicably having a variable appearance during the process. This is particularly troublesome because the mass-baked crystals can be centrifugable and then non-centrifugable at certain times, and this without any prior prediction of its behavior can be realized. There is then a need to recast the cooked masses obtained if it is desired to reuse them in the process and this makes the process impractical and less economical.

However, in order to accelerate the industrial development of D-allulose, which is today mainly marketed in the form of syrup, it is imperative on an industrial scale to be able to produce a continuous and stable process for producing D crystals. -allulose, in order to provide them at a competitive price.

After much research, the Applicant has succeeded in obtaining a method for manufacturing D-allulose crystals in which the problems mentioned above can be solved.

Due to an improved process stability, the production of the crystals does not require systematic control as for example indicated in the document WO 201 1/1 19004, which makes possible the realization of a continuous process for the production of crystalline crystals. D-allulose.

Moreover, since the method of the invention also allows many recycling steps, the efficiency of the process can be greatly increased. It is by conducting numerous investigations that the Applicant has found that, in a process for the manufacture of D-allulose crystals, particular impurities are formed during the different steps of the process for preparing the stock solution. These impurities have, to the best knowledge of the Applicant, never been reported in the literature. They could be identified by the Applicant using a particular technique of gas phase chromatography (GC). Without being bound to any theory, the Applicant believes that these impurities are D-allulose dimers that form through condensation throughout the process.

The Applicant has also been able to show that these dimers of D-allulose, unlike other impurities such as glucose or D-fructose, have a very important anti-crystallizing effect.

Surprisingly, the Applicant has achieved, by carrying out a process for manufacturing D-allulose crystals in which a particular separation step is performed, to eliminate this problem of difficult crystallization of D-allulose. This separation step consists of a nanofiltration step, which allows the elimination of these anti-crystallizing impurities.

This new process presents a major advance for the industrial development of D-allulose crystals since it makes it possible to achieve an overall yield in excess of 25% relative to the introduced D-fructose, advantageously exceeding 50%, or even exceeding 65%. This makes it possible to envisage the manufacture of D-allulose crystals at a competitive price as well as the commercial development of such crystals on a larger scale.

Furthermore, the Applicant has found that the presence of these impurities is a factor that influences the shape of the crystals, especially when one seeks to make large crystals, especially when their average size exceeds 200 μηη.

In its research, the Applicant has also succeeded in manufacturing new D-allulose crystals by using a specific crystallization process using, among the manufacturing steps, the nanofiltration step mentioned above. These crystals, which are another aspect of the present invention, have the particular feature of comprising a mass percentage of very weak D-allulose dimer. The crystals obtained may also have a different shape and an improved flow. These shape and flow properties are directly related to the fact that dimers are present in crystals in very small amounts. On the contrary, when it is desired to make large crystals, the important presence of D-allulose dimers in the stock solution during the crystallization leads to D-allulose crystals comprising significant amounts of these dimers; in addition, the elongation of these crystals is observed to form needles. However, these needle crystals may have a lower flow than the crystals of the invention. Summary of the invention

The invention thus relates to a process for manufacturing D-allulose crystals comprising:

A step of providing a composition rich in D-allulose,

A step of concentration of said solution to form a mother solution to crystallize,

A step of crystallization of the stock solution to form D-allulose crystals and mother liquors;

And at least one nanofiltration step, said step taking place in a step prior to the concentration step of the composition rich in D-allulose.

As mentioned above, the Applicant has found that, consistently, in a process for manufacturing D-allulose crystals, particular impurities are formed during the process. These have, to the best knowledge of the Applicant, never been reported in the literature. This is explained by the fact that, by the high performance liquid chromatography (HPLC) conventionally used to measure the purity of D-allulose, these impurities are not detected on the chromatograms (see Figures 7 and 8). It is by using a gas chromatography technique that the Applicant was able to detect their presence (see FIGS. 9 and 10).

These impurities could be identified by the Applicant as D-allulose dimers. The Applicant has also been able to show that these dimers, unlike other impurities such as glucose or D-fructose, have a very important anti-crystallizing effect. Since these dimers of D-allulose are formed during the process, their presence can limit the yield of a continuous process for the manufacture of D-allulose crystals by preventing this crystallization in a pure and simple manner, by forming cooked masses. non-centrifugable, if the quantities in these dimers are too important. Furthermore, in an industrial and continuous process for manufacturing D-allulose crystals where many successive steps are performed, the amount of these impurities can vary over time. This renders the process unstable over time, the cooked masses sometimes being centrifugable, sometimes non-centrifugable. It is the merit of the Applicant to have identified these specific impurities and to have managed to eliminate them, by performing a separation step of at least partially separating these dimers of D-allulose by nanofiltration.

With the aid of the process of the invention which makes the crystallization step very stable, it is then possible to carry out the process continuously but also drastically increase the overall yield of D-allulose crystals. This is enabled by the fact of being able to provide a stock solution of D-allulose having a very small amount of D-allulose dimers, this thanks to the aforementioned nanofiltration step.

Another merit of the Applicant is to have been able to provide new crystals of D-allulose using this mother solution, in a particular crystallization process which also limits the in-situ formation of said dimers. This results in crystals whose mass percentage of dimers of D-allulose is lower than those of the prior art. Another subject of the invention thus relates to D-allulose crystals comprising a mass content of D-allulose dimer, determined by gas chromatography (GC), of less than 0.5%. As for the crystals described in WO201111004 A2, as they are very fine in size, they are difficult to separate from the mother liquors of crystallization. These mother liquors comprising large amounts of dimers of D-allulose and the content of dimers in the crystals recovered after separation is important, much greater than that of the crystals of the invention. Moreover, Comparative Example 3 of the present Application (see examples) demonstrates that even by further improving the process described in this document, the Applicant has not been able to obtain the crystals of the invention.

As for the crystals described in WO 2016/064087, they have impurities, which may be D-allulose dimers in amounts greater than the crystals of the invention. Without being bound by any theory, the presence of these dimers can be explained by the fact that the D-allulose solution is kept in heat before being introduced into the crystallizer, ie for a period of up to 60 hours. In addition, this document is completely silent on how to prepare the stock solution, particularly with regard to the conditions of the concentration step. However, as it appears in the following description, the choice of the conditions of the crystallization and concentration steps have a significant impact on the amount of D-allulose dimers formed. Thus, the choice of these conditions makes it possible to limit the quantities of dimers formed during the process and thus to reduce the levels of D-allulose dimers in the D-allulose crystals obtained. As the choice of the conditions of the preparation stages of the mother solution have a crucial impact on the The amount of D-allulose dimers therein does not describe either the mother solution useful in the preparation of the crystals of the invention, or the crystals themselves.

EP1860195 discloses complex tubular crystalline compositions of D-allose and D-allulose wherein D-allulose is a minority and not D-allulose crystals.

For crystalline compositions obtained by crystallization in ethanol described in document CN 104447888 A, this document is silent on many process conditions for the manufacture of crystalline compositions and in particular on the concentration step of the stock solution. It is in this respect impossible to reproduce these manufacturing tests of the crystalline compositions. However, it is useful to note that the crystallization must be made specifically in an organic solvent such as ethanol. However, it is known that crystallization in this type of solvent is used only if necessary. Indeed, the water that usually preferred for obvious reasons of costs and environmental. A selected organic solvent (ethanol in the case of D-allulose), although more expensive and imposing difficulties for its reprocessing, has the advantage of facilitating crystallization, making possible a crystallization that would be impossible in water. This therefore confirms that the mother solution of D-allulose comprises large quantities of D-allulose dimers impurities and this can be explained by the fact that no particular precaution for the various steps of preparation of the mother solution seems to have been achieved (in particular no condition is indicated for the concentration stage). On the other hand, in terms of purification, crystallization in ethanol may be less effective in obtaining crystals of high purity of D-allulose than crystallization in water (when this is possible) because these dimers of chemical nature close to D-allulose are also sparingly soluble in ethanol and also precipitate. Finally, other impurities also numerous are found in the crystalline compositions as demonstrated by the low purities obtained in this document. Crystalline compositions obtained by crystallization in ethanol are also described in the publication by Takeshita et al. (Mass production of D-psicose from D-fructose by a continuous bioreactor using immobilized D-tagatose 3-epimerase, Journal of Bioscience and Bioengineering, Vol.90 No. 4, January 2000, pp. 453-455). This document focuses on the first step of preparation of D-allulose and not on the manufacture of D-allulose crystals which are also very little detailed. Since the choice of the conditions of the preparation steps of the mother solution have a major impact on the amount of D-allulose dimers therein, this document does not describe the mother solution useful for the preparation of the crystals of the invention. neither the crystals themselves. Moreover, in this document, it is specified that this crystallization is carried out in ethanol to facilitate the solidification of D-allulose, which demonstrates the quantity significant non-crystallizing impurities and confirms the impossibility of crystallizing the stock solution of D-allulose of this document in water. Moreover, the crystallization in question in this document is in fact a "precipitation" not controlled by addition of ethanol, inevitably leading to impure crystalline solid compositions.

Other crystalline compositions are also mentioned in the document CN 103333935 A but without any details of their preparation since no condition of preparation of the stock solution or crystallization (not even solvent) are indicated. Moreover, this document does not include a preparation test itself. Since the choice of the conditions of the preparation steps of the mother solution have a major impact on the amount of D-allulose dimers therein, this document does not describe the mother solution useful for the preparation of the crystals of the invention. neither the crystals themselves. On the other hand, the low purities of the crystalline compositions obtained (98%) in this document seem to indicate that the crystalline compositions are very impure. Another object of the invention also relates to the use of a nanofiltration unit in a D-allulose crystal production circuit to improve the overall yield of D-allulose crystals.

Brief description of the Figures

Figure 1: Figure 1 schematically shows a D-allulose crystal production circuit in which the D-fructose rich chromatography raffinate is recycled to be mixed with the fructose at the top of the epimerization reaction.

Figure 2: Figure 2 schematically shows a D-allulose crystal production circuit in which the crystallization mother liquors are recycled to be mixed with the composition of D-fructose / D-allulose resulting from the epimerization reaction.

Figure 3: Figure 3 schematically shows a D-allulose crystal production circuit comprising a nanofiltration unit useful in the method of the invention.

Figure 4: Figure 4 shows an example of vacuum crystallizer adiabatic evaporator useful for a variant of the method of the invention.

Figure 5: Figure 5 shows an example of vertical crystallizer useful to a variant of the method of the invention. Figure 6: Figure 6 shows the permeation curve relative to the nanofiltration step, that is to say the flow as a function of the volume concentration factor.

Figure 7: Figure 7 shows an HPLC chromatogram of a composition rich in D-allulose removed in the method of the invention (see Figure 3), that is to say before nanofiltration.

Figure 8: Figure 8 shows an HPLC chromatogram of a permeate taken from the process of the invention (see Figure 3), that is to say after nanofiltration.

FIG. 9: FIG. 9 represents a GPC chromatogram, in the dimer characteristic zone, of a composition rich in D-allulose taken from the process of the invention (see FIG. 3), that is to say before nanofiltration. .

Figure 10: Figure 10 shows a chromatogram CPG, in the characteristic zone of dimers, a permeate taken from the process of the invention (see Figure 3), that is to say after nanofiltration.

FIG. 11: FIG. 11 represents a photograph obtained by optical microscopy of comparative D-allulose crystals.

Figure 12: Figure 12 shows two photographs obtained by optical microscopy of D-allulose crystals according to the invention.

Figure 13: Figure 13 shows a photograph obtained by light microscopy of D-allulose crystals manufactured and marketed by CJ CheilJedang Food Ingredient.

Figure 14: Figure 14 shows the ratio of Feret min / Feret max diameters as a function of volume particle size D4,3 for two types of D-allulose crystals.

Figure 15: Figure 15 represents the diameters Feret min and Feret max of a model particle.

Detailed description of the invention

A process for manufacturing D-allulose crystals conventionally comprises:

A step of concentrating a composition rich in D-allulose to provide the mother solution to be crystallized;

A step of separation of the mother liquors and crystals of D-allulose.

The method of the invention has the particularity of comprising a nanofiltration step. This nanofiltration step makes it possible to limit the amount of D-allulose dimers in the mother solution provided in the process of the invention. This nanofiltration step takes place in a step prior to the concentration step of the composition rich in D-allulose. This step therefore allows the supply of a stock solution of D-allulose whose D-allulose dimers content is lower than that obtained from the same process not using this nanofiltration step.

In the nanofiltration step, which is essential to the process of the invention, two fractions are formed when a nanofilter D-allulose composition is subjected to:

A permeate, which is depleted in D-allulose dimers;

· As well as a retentate, which is enriched in D-allulose dimers.

In Figure 3 which shows a crystal production circuit useful for the process of the invention, Flux 6 represents the permeate and Flux 12 represents the retentate. For illustrative but not limiting reasons, the flows indicated in the following description refer to the flows of the production circuit of this FIG.

The nanofiltration permeate is an intermediate for the manufacture of this mother solution.

The terms "depleted of D-allulose dimers" and "D-allulose dimeric enriched" are obviously relative to the D-allulose oligomer content of the nanofilter composition. By "D-allulose dimer" is meant a compound comprising a D-allulose condensed with at least a second identical or different monosaccharide. These dimers are, for example, D-allulose-D-allulose type dimers.

These dimers could be detected by GPC and could not be detected during HPLC analysis, as demonstrated in the examples section. It follows that the mass quantities of the various constituents, expressed in dry mass, are in the present application systematically determined by GPC. To determine the amounts of each of the species in the composition, the sample generally undergoes a treatment step in order to transform the various species present into trimethylsilylated methoxim derivatives. The mass quantities of each of the species are expressed in the present application, unless otherwise indicated, with respect to the total dry mass.

The amounts of glucose, fructose and allulose can be determined in a gas chromatograph equipped with an injector heated to 300 ° C, a flame ionization detector (FID) heated to 300 ° and equipped with a capillary DB1 column of 40 meters, having an internal diameter of 0.18 mm and a film thickness of 0.4 μηη, the the temperature of the column being programmed as follows: from 200 ° C. to 260 ° C. at a rate of 3 ° C./min, then from 260 ° C. to 300 ° C. at 1 ° C./min. at 300 for 5 min.

By quantity of dimers of D-allulose is meant the difference between the total amount of dimers in a sample, determined by GPC, and the amount of known dimers that may be present, which are glucose-glucose dimers such as maltose and isomaltose. However, the amount of these glucose-glucose dimer is generally very low or nonexistent. For example, in the mother solution useful in the invention, the mass quantity of glucose-glucose dimer is generally less than 0.2%, often less than 0.1%. It is the same with the crystals of the invention.

The possible amount of glucose-glucose dimer can be determined under the same conditions as those described above for glucose, fructose and D-allulose:

• performing hydrolysis of the glucose-glucose dimer of the sample;

• by determining the amount of total glucose in the same chromatograph and under the same conditions, said total glucose comprising the initial glucose said free and the glucose from the hydrolysis of glucose-glucose dimer;

• subtracting, from this amount of total glucose, the amount of initial glucose in the sample.

The total amount of dimer can in turn be determined in a gas chromatograph under the same conditions as previously described, with the difference that the column used is a capillary DB1 column of 30 meters, having an internal diameter of 0.32 mm. and 0.25 μηη film thickness and the column temperature is programmed as follows: 200 to 280 C ^q ^ at 5 ° C / m \ n, ^q maintaining at 280 C for 6 min and then 280 ° C up to 320 ^q C to 5 ° C / m \ n, hold at 320 for 5 min.

The method is described in more detail in the Examples section.

In order to carry out the nanofiltration step that is useful for the invention, the nanofiltration composition is passed over a nanofiltration membrane. It generally has a dry matter ranging from 5 to 15%.

The temperature of this composition nanofiltrer can range from 10 to 80 ° C, usually 15 to 50 ° C, often around 20 ^q C.

Those skilled in the art will be able to choose the membrane useful for this separation. This nanofiltration membrane may have a cut-off threshold of less than 300 Da, preferably ranging from 150 to 250 Da. Ideally, the membrane has a MgSO4 rejection rate of at least 98%. It may especially be a membrane Dairy DK type or Duracon NF1 manufactured by GE ^® . The pressure applied to the membrane may also vary widely and may range from 1 to 50 bar, preferably from 5 to 40 bar, most preferably from 15 to 35 bar.

This nanofiltration step may be accompanied by a diafiltration phase.

Preferably, the volume concentration factor (FCV) of the nanofiltration ranges from 2 to 20. This volume concentration factor is easily adjusted by the person skilled in the art.

This nanofiltration step can be carried out continuously.

According to the invention, the step of providing a composition rich in D-allulose can comprise:

A step of providing a composition comprising D-fructose (Flux 1 or 1 ');

An epimerization step to form a composition comprising D-fructose and D-allulose (Flux 2);

A chromatography step to provide a composition rich in D-allulose (Stream 5) and a raffinate, which is a composition rich in D-fructose (Flux 14).

Preferably, the nanofiltration step is performed between the step of providing the D-allulose rich composition (Stream 5) and the concentration step to provide the D-allulose stock solution (Stream 7). The nanofiltration step of said composition rich in D-allulose provides a retentate (Flux 12) and a permeate (Flux 6).

Thus, a variant of the preferred embodiment of the invention which comprises:

A step of providing a composition rich in D-allulose;

A nanofiltration step of said composition rich in D-allulose to provide a retentate and a permeate;

A nanofiltration permeate recovery step;

A concentration step of this permeate to provide the stock solution of D-allulose.

In the process of the invention, the nanofiltration step is thus advantageously carried out on the composition rich in D-allulose resulting from the chromatography step, just before the concentration step which provides the stock solution. It is in this configuration that the process makes it possible most effectively to limit the quantity of D-allulose dimers in the mother solution to be crystallized, and therefore to increase the overall yield of crystals of D-allly. allulose.

By composition rich in D-allulose, generally means a composition having in dry mass a mass content of D-allulose greater than 80%, preferably ranging from 80 to 99%, preferably 82 to 98%. As regards the permeate obtained, its dry matter may vary, for example in the range from 3 to 15%. The permeate may in particular comprise, in addition to D-allulose, D-fructose and glucose, as well as other sugars that may be present. The composition of this filtrate can be very different and depends on the nanofilter composition. At the end of this nanofiltration step, the recovered permeate may comprise, relative to its dry mass, from 0 to 1.2% D-allulose dimers, for example from 0.1 to 1.0%, in particular from 0.15 to 0.5%. The permeate may be subjected to one or more steps such as a mixing step with an additional product, a separation step, a purification step, an epimerization step or a concentration step.

With regard to the retentate obtained, its dry matter may also vary widely, for example in the range of 15 to 40%. It may comprise mainly D-fructose, D-allulose, glucose and D-allulose dimers. According to one variant, the retentate is recovered, optionally mixed with an additional composition of D-allulose, to provide, after a possible concentration step, a syrup of D-allulose.

In the preferred variant in which the D-allulose-rich composition which comprises D-allulose dimers is subjected to a nanofiltration step, the permeate obtained (Stream 6), referred to as "preferred permeate", preferably comprises in dry mass:

80 to 99% of D-allulose;

0 to 20% of D-fructose;

0 to 10% glucose;

From 0 to 1, 2% D-allulose dimers.

As indicated above, this preferred permeate can be directly subjected to a concentration step to obtain the stock solution to be crystallized (Stream 7).

It is specified that in the present application, apart from D-allulose crystals, all the compositions are generally aqueous compositions. In other words, the solvent of the dry constituents comprises water. The solvent of the compositions is generally water or a mixture of water and alcohol such as, for example, ethanol. Preferably, the solvent of the compositions is water.

Thus, the D-allulose stock solution useful in the invention generally consists of an aqueous solution of D-allulose. The stock solution generally has a solids content of at least 75%, for example 80 to 95%, preferably 81 to 92%, most preferably 83 to 89%. To reach this dry matter, it is necessary to carry out a concentration step. This step can be performed on a composition rich in D-allulose, the only requirement is that this composition rich in D-allulose was obtained by a process comprising, in an earlier step, the nanofiltration step useful to the invention. This composition rich in D-allulose subjected to the concentration step can thus be the preferred permeate described above, but also a composition rich in D-allulose obtained by chromatography, or a mixture of a permeate with a composition rich in D - additional allulose. Preferably, the composition rich in D-allulose subjected to the concentration step is the preferred permeate.

The formation of D-allulose dimers also occurring during the concentration step, it is preferable to select conditions to limit the amounts formed in these dimers. The concentration step is thus generally carried out under vacuum, for example at a pressure of 5 to 100 mbar, preferably ranging from 20 to 70 mbar. This vacuum makes it possible to reduce the temperature necessary for evaporation and to reduce the duration of this concentration step. It can be carried out at a temperature ranging from 30 to 80.degree. C., advantageously from 34 to 70%, preferably from 37 to 50.degree. This concentration step can be carried out in a single-stage evaporator, a multi-stage evaporator, for example a double-stage evaporator. At the end of the concentration step, the D-allulose stock solution that is useful for the invention is obtained.

This concentration step can be carried out continuously.

The mother solution obtained can comprise in dry mass:

From 80 to 99% of D-allulose, preferably from 85 to 98%;

From 0 to 20% of D-fructose, preferably from 0.5 to 15%;

0 to 10% glucose, preferably 0 to 5%;

From 0 to 1.5% dimers of D-allulose, for example from 0.1 to 1.2%, preferably from 0.4 to 1.1%.

The method according to the invention further comprises a step of crystallizing said D-allulose stock solution to form a suspension of D-allulose crystals. This suspension comprises crystals and mother liquors of crystallization which are also formed during this step.

This crystallization step can be of any type. It may especially be a cooling crystallization step or an evapocrystallization crystallization step. The skilled person will find the conditions of implementation which are described in particular in WO 201 1/1 19004. However, it should be noted that the crystallization steps described in these documents are made easier to achieve because of the particular preparation of the mother solution useful for the invention.

At the end of the crystallization step, from the suspension of crystals (Flux 9) the crystals (Flux 10) are separated from the mother liquors (Flux 13), in particular by a filtration and / or centrifugation step. This separation step is more preferably in batch.

The mother liquors (flux 13) generally have a solids content ranging from 70 to 80%. They can include in dry mass:

From 80 to 99% of D-allulose, preferably from 82 to 95%;

From 0 to 20% of D-fructose, preferably from 0.5 to 15%;

0 to 10% glucose, preferably 0 to 5%;

From 0 to 3% D-allulose dimers, for example from 0.1 to 2.9%, especially from 1 to 2.5%.

The crystals obtained can be subjected to a step of clearing with cold water and / or alcohol, especially ethanol. These crystals can then be dried (Flux 1 1) by a drying step that can be done in any type of suitable dryer. The D-allulose crystals have a water content of less than 5%, preferably less than 1%.

This crystallization step can be carried out continuously, in particular using a vertical crystallizer, an example of which is shown in FIG. 5.

In a most preferred embodiment, the crystallization step comprises an adiabatic evaporative cooling step, carried out in an adiabatic evaporator-evaporator under vacuum to form a mass-cooked product (Stream 8), followed by a cooling crystallization stage. of said massecuite to provide a suspension of crystals (Flux 9). An adiabatic evapo-cooling causes an immediate cooling of the stock solution to crystallize. Preferably, the crystallizer-evaporator is equipped with a condenser and the condensed water during this stage is reinjected continuously along the walls at the top of the crystallizer to maintain stable dry matter. This preferred crystallization step comprising two distinct stages, combined with the nanofiltration step in a particular configuration of the process of the invention, made it possible to continuously obtain the crystals of the invention which are described below in the description. . This is related to the fact that this preferred crystallization step, especially the evapo-cooling stage, also makes it possible to very significantly limit the in-situ formation of D-allulose dimers. Without being bound to any theory, the Applicant explains it by the fact that the mother solution can be cooled by virtually instantaneous manner when it is introduced into the crystallizer-evaporator, unlike the already known crystallization processes of D-allulose, which describe the natural cooling of the stock solution, or even by a cooling ramp with the aid of a heat exchanger of heat as described in WO2016 / 064087. The crystals according to the invention have improved purity and properties, although the first stage of the crystallization step is an instant evaporative cooling step, which shortens the duration of the crystallization step. However, this is contrary to what would be envisaged by those skilled in the art, for whom obtaining improved crystals requires an increased crystallization time.

In the evapo-cooling stage, the temperature can range from 30 to 40 ° C, preferably from 33 to 37 ° C, for example about 35 ° C. This temperature is easily reached by those skilled in the art by determining the adequate depression to be applied. Thus, the pressure in the crystallizer-evaporator can range from 30 to 50 mbar. An adiabatic crystallizer may in particular be a crystallizer type DT draft tube (Draft tube) or type DTB (Draft Tube Baffle), forced circulation or indirect forced circulation (IFC ^® ). Preferably, this evapo-cooling stage is continuous. At this stage, the primers are generated continuously by spontaneous nucleation phenomenon in the evapo-crystallizer by the supersaturation created by the rapid cooling; thus, there is no proper introduction of primers in this case. Without limitation, a possibility of carrying out this continuous evapo-cooling stage is described in the Examples section and in FIG. 4, where a fraction of the crystals formed during the evapo-cooling stage (Flux 7d) is mixed. in the feed stream 7b of the crystallizer-evaporator, which makes it possible to obtain a stream 7c which comprises, at the time of introduction into the crystallizer-evaporator, crystals which will be able to be further enlarged during this new passage through the crystallizer-evaporator. According to this example, Flux 7b can be obtained from a mixture of Flux 7 and Flux 7a, which consists of a supersaturated syrup of D-allulose recovered in the crystallizer-evaporator, which comprises "fines", c that is, the finest crystals of D-allulose from the crystallizer. According to this variant, Flux 7 can advantageously, before mixing, pass into a heat exchanger, this passage allowing to warm up Flux 7 almost immediately before mixing it immediately with Flux 7a. This then makes it possible to remelt the fines of the Flux 7a and to cool the Flux 7 to obtain a Flux 7b free of these fines.

At the end of this stage, a mass-cooked D-allulose crystal (Flux 8), that is to say a suspension of crystals, generally having a small size, is recovered. The average residence time of the massecuite during this evaporative cooling stage can be between 5 and 15 hours. The average volume size D4,3 of the crystals suspended in the massecuite generally ranges from 50 to 200 μηη.

The cooling crystallization stage is carried out in a conventional manner by cooling the massecuite obtained during the evapo-cooling stage (Stream 8). The duration of this crystallization stage can range from 25 to 50 hours. The crystallization start temperature generally depends on the temperature of the introduced filler and may especially range from 30 to 40%, preferably from 33 to 37%, for example about 35%. This stage is usually done with mechanical stirring. Preferably, during cooling crystallization, the temperature is decreased at a rate of 0.3 to 0.5 ° C per hour. Figure 5 shows an example of a vertical crystallizer with, on the sides, different heat exchangers for adjusting the temperature in the crystallizer. During this operation, it is preferred that the temperature difference between the massecuite and the water of the exchanger does not exceed 5 ° C. The cooling crystallization stage may preferably be carried out continuously, in particular in a vertical crystallizer.

Thus, a preferred variant of the method of the invention comprises:

A step of providing a composition rich in D-allulose (Stream 5);

A nanofiltration step of said composition rich in D-allulose to provide a retentate (Flux 12) and a permeate (Flux 6);

A nanofiltration permeate recovery step;

A step of concentration of this permeate to provide the stock solution of D-allulose (Stream 7);

A crystallization step comprising:

i. an adiabatic evapo-cooling stage, carried out in an adiabatic evaporator-evaporator under vacuum to form a mass-cooked product (Flux 8),

ii. followed by a crystallization stage by cooling said massecuite to form a crystal suspension (Flux 9).

Apart from the advantages related to the crystals themselves, an advantage of this preferred variant of the process of the invention is that the crystals obtained can be more easily separated from the mother liquors of crystallization and more easily dried. This is mainly related to the shape of the crystals obtained.

To start a crystallization step, D-allulose primers are generally introduced into the selected crystallizer. These D-allulose primers consist of D-allulose crystals of small size, for example having a size ranging from 10 to 100 μηη. The mass amount of primer can vary widely depending on the type of crystallizer used. It can range from 0.001 to 1%, often from 0.01 to 0.7%, generally from 0.05 to 0.5% relative to the mass of D-allulose in the stock solution. These amounts are particularly suitable when a crystallization step is carried out by cooling from a stock solution of D-allulose. As mentioned above, it is also possible to create primers in situ when using an evapo-cooling step.

Preferably, the crystallization step is carried out less than one hour after the concentration step, preferably less than 30 minutes later. Most preferably, the crystallization step is carried out immediately after the concentration step. This makes it possible to further limit, at the time of the crystallization step, the quantity of dimers in the mother solution to be crystallized.

Once recovered after drying, the crystals may also be subjected to an additional sieving step, which makes it possible to screen these crystals and, depending on the fraction recovered after sieving, to increase or decrease the size of the crystals. For example, this additional step makes it possible, relative to the size of the crystals subjected to the sieving step, to recover a fraction of smaller average size in volume D4,3 of crystals of D-allulose passed through the sieve as well as a larger average volume fraction D4.3 of D-allulose crystals remaining in the sieve. To modify the crystal population and obtain the desired fraction D 4.3, it is sufficient for a person skilled in the art to select the mesh size of the sieve.

It goes without saying that the method according to the invention may comprise other steps, such as the other steps in the conventional method described above and which will be described in detail later. The process according to the invention may also comprise additional purification steps and also intermediate dilution or concentration steps in order to regulate the dry matter and thus perform the various steps of the process of the invention under the best conditions. All of these steps can be performed continuously.

The D-fructose composition provided (Stream 1) for carrying out the epimerization step can be a D-fructose syrup, which can be obtained by dissolving D-fructose crystals in water or a glucose syrup. / D-fructose. Preferably, this composition comprises a glucose / D-fructose syrup which comprises at least 90% by dry weight of D-fructose, preferably at least 94% of D-fructose. In a preferred mode that will be explained later in the description, the D-fructose composition provided to carry out the subsequent epimerization step is a mixture (Flux 1 ') of this D-fructose syrup with at least one recycled fraction which may be the raffinate in whole or in part (Flow 14 or 16), this recycled fraction may comprise a higher amount of D-allulose.

The D-fructose composition subjected to the epimerization step may comprise:

0 to 10% of D-allulose;

• 70 to 100% D-fructose;

• 0 to 10% glucose;

0 to 15% D-allulose dimer.

The epimerization step is carried out from the D-fructose composition provided above, optionally after adjusting the dry matter. This step is generally carried out at a solids content ranging from 30 to 60%, often from 45 to 55%. A D-psicose epimerase type enzyme or a composition comprising this enzyme is introduced into this composition. The composition comprising this enzyme may be a lyophilizate of a host microorganism synthesizing D-psicose epimerase, which may be Bacillus subtilis, in particular that described in application WO2015 / 032761 A1. The pH is adjusted according to the enzyme used, for example at a pH ranging from 5.5 to 8.5. The reaction may be carried out by heating at a temperature ranging from 40 to 70 ^q C, often from 45 to 60 ° C. The reaction may last from 0.1 to 100 hours, for example from 0.2 to 60 hours. This reaction can for example be done on an enzyme column, which has the advantage of also working continuously on this step. It is also possible to work continuously working sequentially with multiple reactors. To carry out this epimerization stage, it is particularly possible to use the teaching of document WO 2015/032761 A1.

At the end of the reaction, a composition comprising D-fructose and D-allulose is formed, generally in a mass ratio D-fructose / D-allulose ranging from 85/15 to 55/45, often in a mass ratio D -fructose / D-allulose ranging from 80/20 to 60/40. This ratio depends on the epimerization parameters used and, of course, on the amount of D-allulose and D-fructose in the D-fructose composition provided in the epimerization step; the amount of D-allulose in this composition may be particularly important in case of recycling. At the end of this epimerization step, if necessary, a filtration step may be performed to recover any cell debris present, especially when a lyophilizate of a host microorganism is used. This step may consist of a microfiltration step. In Figure 3, the microfiltered composition corresponds to Stream 3 and the cellular debris is recovered in Stream 17.

In the process of the invention, additional purification steps can also be performed. Before the chromatography step, a demineralization step is generally carried out for the composition comprising D-fructose and D-allulose (Flux 3), which can be carried out by passage through one or more cationic ion exchange resins (for example a cationic resin of the Dowex 88 type), anionic (for example an anionic resin of the Dowex 66 type) and a cationic-anionic mixture. In FIG. 3, this composition corresponds to Stream 4. The composition comprising D-fructose and D-allulose obtained is then demineralized and generally has a resistivity of greater than 100 kΩ.crrv ¹ . It is also possible to carry out, prior to this demineralization step, a step of bleaching the composition comprising D-fructose and D-allulose, for example by passing over a column comprising activated carbon.

The composition comprising D-fructose and D-allulose (Stream 4) can then be subjected to a chromatography step to provide at least one composition rich in D-allulose and a composition rich in D-fructose. In a preferred embodiment which will be explained in detail later in the description, the composition comprising D-fructose and D-allulose subjected to the chromatography step is a mixture (Flux 4 ') of the composition resulting from the step epimerisation (Flux 4) and at least one recycled fraction, this recycled fraction may comprise a higher amount of D-allulose.

The composition subjected to the chromatography step can comprise, with respect to its dry mass:

• from 22 to 45% of D-allulose, usually from 25 to 37%;

• 45 to 75% D-fructose, usually 46 to 70%;

0 to 10% glucose;

• 2 to 10% D-allulose dimer.

To carry out this chromatography step, it is possible to use any type of continuous chromatography, in particular of the Simulated Moving Bed SMB type, of the Improved Simulated Moving Bed (ISMB) type, of the Divide Improved Simulated Moving Bed type (DISMB). ), Sequential Simulated Moving Bed (SSMB) or Nippon Mitsubishi Chromatography Improved (NMCI) type. Water is generally used as an eluent. The chromatography can be equipped with several columns in series, for example from 4 to 8 columns. The columns comprise ion exchange resin, for example a resin cationic ion exchange calcium. The dry matter of the composition comprising D-fructose and D-allulose can range from 40 to 70%, generally about 50%. The temperature of the composition during the chromatography is generally from 40 to 80 ° C, preferably from 55 to 65 ° C. This chromatography lasts the time to obtain a satisfactory separation and can last several hours.

At the end of this step, a composition rich in D-allulose (Stream 5) is obtained which may comprise, relative to its dry matter, at least 80% of D-allulose, advantageously at least 90% of D-allulose. This composition rich in D-allulose can have a dry matter ranging from 5 to 15%. At the end of this step, a raffinate (Flux 14) is also obtained, which generally comprises, with respect to its dry matter, at least 75% of D-fructose, often at least 80% of D-fructose. This raffinate generally has a solids content ranging from about 15 to 30%.

The composition rich in D-allulose obtained at the end of the chromatography (Stream 5) can thus comprise, with respect to its dry mass:

From 80 to 98% of D-allulose;

0 to 20% of D-fructose;

• 0 to 10% glucose;

1.5 to 5% D-allulose dimer.

The raffinate can include meanwhile, in relation to its dry mass:

From 1 to 10% of D-allulose;

• from 70 to 99% of D-fructose;

• 0 to 10% glucose;

• 5 to 20% D-allulose dimer.

Unlike a conventional process where, relative to the D-fructose introduced, the overall yield of D-allulose crystals is less than 15%, the yield of the process of the invention may be greater than or equal to 25%. Advantageously, the overall yield of D-allulose crystals is greater than or equal to 50%, for example greater than or equal to 60%, or even greater than or equal to 65%. This particularly improved yield is made possible by the fact that it is possible to carry out recycling steps without disturbing the crystallization step.

Thus the method of the invention may comprise at least one recycling step.

According to a preferred embodiment, this recycling step may consist of a step of recycling at least a portion of the raffinate resulting from the chromatography step (Stream 14). This raffinate can possibly have been concentrated before being mixed. It may advantageously be recycled, in whole or in part, to be mixed with D-fructose (Flux 1), for example in the form of the glucose D-fructose syrup described above, to provide the D-fructose composition (Flux 1 '). It is then this D-fructose composition, which is generally richer in D-allulose than the D-fructose syrup, which is subjected to the epimerization step.

This recycling step may consist of a step of recycling at least a portion of the mother liquors (Flux 13). These mother liquors may advantageously be recycled, in whole or in part, to be mixed with the composition comprising D-fructose and D-allulose (Flux 4). It is then this mixture (Flux 4 ') which is subjected to the chromatography step. These mother liquors may possibly have been diluted before being mixed.

This recycling step may consist of a step of recycling at least a portion of the retentate (Stream 12). This retentate may advantageously be recycled, in whole or in part, to be mixed with the composition comprising D-fructose and D-allulose (Flux 4) and optionally recycled mother liquors. It is then this mixture (Flux 4 ') which is subjected to the chromatography step. This retentate may possibly have been concentrated before being mixed. In the case where the mixing is with the retentate and mother liquors, it may not be necessary to concentrate or dilute these fractions. It should be noted that the retentate and mother-water fractions, which are two fractions with relatively large amounts of D-allulose, make it possible to increase the richness of D-allulose (and consequently reduce the amount of D-fructose). of the composition subjected to the chromatography step.

To carry out the possible steps of concentration of recycled fractions, it is possible to use the same equipment and conditions described for the concentration step for the manufacture of the stock solution.

According to a most preferred embodiment of the invention (FIG. 3 represents a production circuit for this preferred method of the invention), the method comprises:

a) a step of providing a composition comprising D-fructose (Stream 1 ');

b) an epimerization step to form a composition comprising D-fructose and D-allulose (Stream 2);

c) a chromatography step to provide a composition rich in D-allulose (Stream 5) and a raffinate consisting of a composition rich in D-fructose (Stream 14);

d) a nanofiltration step of the composition rich in D-allulose to form a permeate (Stream 6) and a retentate (Stream 12); e) a permeate concentration step to form the mother solution to be crystallized (Flux 7);

f) a step of crystallization of the stock solution (Flux 9) to form crystals (Flux 10) and mother liquors (Flux 13);

and in which is realized:

A step of recycling at least a portion of the raffinate (Flux 14 or 16) to be mixed with D-fructose (Stream 1) and to provide the composition (Flux 1 ') of step a);

And / or a step of recycling at least a portion of the retentate (Flux 12) resulting from the nanofiltration step to be mixed with the composition comprising D-fructose and D-allulose (Flux 4) resulting from the step b) to provide the composition (Flux 4 ') subjected to the chromatography step c);

And / or a step of recycling at least a portion of the mother liquors (Flux 13) from the crystallization step to be mixed with the composition comprising D-fructose and D-allulose resulting from step b ) (Stream 4) to provide the composition (Flux 4 ') subjected to chromatography step c).

The method comprises a purge step, this purge step may be a purge step of at least a portion of at least one of the recycled fractions selected from raffinate, retentate and mother liquors of crystallization. Indeed, in order for the system to remain stable, it is absolutely necessary to remove from the production circuit part of the D-allulose dimers formed during the process. In general, the more the fractions are recycled, the more the amount of D-allulose dimers increases in the circuit. Thus, a possibility of decreasing the amount of D-allulose dimers is to increase the quantities purged. However, this is done to the detriment of the overall yield of D-allulose crystals. The process of the invention makes it possible to drastically increase the recycling of the various fractions obtained in the process, while maintaining crystallization.

By way of example, in the variant of the all-preferred process described above in which all the raffinate, retentate and mother liquor fractions are recycled, the raffinate recycling step is advantageously a partial recycle, for example 50 to 95% of this raffinate is recycled (Stream 16) and 5 to 50% is purged (Stream 15) to provide a D-fructose composition which includes D-allulose dimers: in other words, the recycling of the composition rich in D-fructose ranges from 50 to 95%. Preferably, the recycling rate ranges from 70 to 92%. In this case, the other two recycling are advantageously total recycling. The purged fractions can then be used to make syrups, optionally after a concentration and / or mixing step with other compositions and / or additives.

Because the crystallization step remains stable over time, the process according to the invention is particularly advantageous because it can be continuous.

As explained above, according to the preferred variant of the invention combining the nanofiltration and crystallization step in a crystallizer-adiabatic vacuum evaporator, the Applicant has also succeeded in obtaining crystals having improved quality.

The crystals according to the invention have a mass content of D-allulose dimer of less than 0.50%, preferably less than 0.30%, or even less than 0.20%. These crystals may advantageously comprise a mass content of D-allulose dimer ranging from 0.01 to 0.48%, preferably ranging from 0.02 to 0.45%, for example ranging from 0.03 to 0.40%. in particular from 0.04 to 0.30%, particularly from 0.05 to 0.20%.

The crystals according to the invention advantageously have a mass content of D-allulose greater than or equal to 99.00%, preferably greater than or equal to 99.50%, or even greater than or equal to 99.70%.

An advantage of the crystals of the invention is that these crystals have low amounts of D-allulose dimer. Without being bound by any theory, the Applicant explains that the mother solution useful for the manufacture of these crystals comprises a very low content of dimers of D-allulose and in that the crystallization step is carried out. This work makes it possible to limit the formation of these dimers in situ. These crystals have thus been obtained by the Applicant by this method, by combining the nanofiltration step with the crystallization step comprising an adiabatic evapo-cooling stage and a cooling crystallization stage.

A disadvantage associated with D-allulose crystals of the prior art, which comprise a dimer content higher than those of the invention, is that an elongation of these crystals is observed to present a shape close to needles, especially when they are large.

Preferably, the D-allulose crystals of the invention have a mean volume size D4,3 greater than 200 μηη, advantageously ranging from 210 to δθθμηη, preferably from 220 to 350 Mm.

The crystals of the invention, which have a lower D-allulose dimer content, have the advantage of having a more "squat" shape, as demonstrated in FIGS. 11, 12 and 13. This more squat form may result in the fact that the D-allulose crystals of the invention may have, for a particle size in volume D 4.3 given and chosen in the range from 200 to 400μηη, a ratio of Feret min / Feret max diameters greater than 0.60, advantageously ranging from 0.62 to 0.90, for example from 0.63 to 0.80. The diameter Feret is a size well known to those skilled in the art. It is deduced from the projected area of a particle, using the vernier caliper principle. The diameter Feret min consists of the smallest dimension while the diameter Feret max consists of the largest dimension. Figure 15 shows the principle of Feret diameters min and max on a given particle.

Preferably, the crystals of the invention have this ratio Feret min / Feret max over all particle sizes in the range from 200 to 400μηη.

In an alternative manner and independently of the content of dimers of D-allulose, an object of the invention relates to D-allulose crystals which have a mean volume size D4,3 greater than 200 μηη, advantageously ranging from 210 to 800μηη. , preferably from 220 to 350 μηη and having, for a particle size in volume D 4.3 given and chosen in the range from 200 to 400μηη, a ratio of Feret min / Feret max diameters greater than 0.60, advantageously from 0.62 to 0.90, for example from 0.63 to 0.80. Preferably, the crystals of the invention have this ratio Feret min / Feret max over all particle sizes in the range from 200 to 400μηη. These crystals of the invention advantageously comprise a mass content of D-allulose dimer of less than 0.50%, preferably less than 0.30%, or even less than 0.20%. These crystals may advantageously comprise a mass content of D-allulose dimer ranging from 0.01 to 0.48%, preferably ranging from 0.02 to 0.45%, for example ranging from 0.03 to 0.40%. in particular from 0.04 to 0.30%, particularly from 0.05 to 0.20%. These crystals advantageously have a mass content of D-allulose greater than or equal to 99.00%, preferably greater than or equal to 99.50%, or even greater than or equal to 99.70%.

The average volume size D4.3 as well as the Feret min / Feret max diameter ratio of the crystals are determined by a particle size analyzer, especially the QICPIC RODOS type granulometer of the SympaTEC brand as used in the Examples section. Since the crystals are statistically observed in all directions in a granulometer, the values obtained by a granulometer for a population of crystals are different from the values obtained by calculation on a simple microscopic plate of this population of crystals, the values obtained by grain size being generally higher. Preferably, the crystals are non-agglomerated (or individualized). The fact that the crystals are unagglomerated can be verified by simple observation by optical microscopy. By way of example, the crystals of FIG. 13 are agglomerated, unlike those of FIGS. 11 and 12.

This different shape is reflected at the macroscopic scale by an improved flow of the crystals of the invention in comparison with crystals of the same average size. Also, these crystals may exhibit better caking behavior over time.

Thus, because of their properties, the crystals obtained by the preferred method of the invention can flow easily. This is how they made it possible to obtain crystals with a flow never reached so far. They can thus be used, for example, advantageously as table sugar.

The D-allulose crystals of the invention can be used in the known applications of allulose and, in general, sweeteners. Among the applications that can use the D-allulose crystals of the invention may be mentioned chewings-gums in the form of tablets or dragees, sweets and sucking tablets, cookies, cookies, muffins, cakes, cookies, gelatin cakes, chewing pastes including short textured cheeses, icings and powdered beverages.

Another object of the invention also relates to the use of a nanofiltration unit in a D-allulose crystal production circuit to improve the process stability and / or the overall yield of D-allulose crystals. This use is particularly advantageous when the raw material introduced into the circuit comprises D-fructose.

Another object of the invention also relates to the use of a nanofiltration unit in a D-allulose crystal production circuit to improve the quality of the crystals obtained. By improving the quality of the crystals obtained, the aim is in particular to reduce the D-allulose dimer content and / or to increase the ratio of Feret min / Feret max diameters of the D-allulose crystals.

By way of illustration, other embodiments of the method according to the invention, comprising a mother liquor recycling step and / or a raffinate recycling step and / or a retentate recycling step are presented hereinafter.

According to a first embodiment, the method comprises:

a) a step of providing a composition rich in D-allulose;

b) a concentration step for forming the mother solution to crystallize;

characterized in that At least one recycling step consists of a step of recycling at least a portion of the mother liquors;

The nanofiltration step is carried out on these recycled mother liquors to form a permeate and a retentate;

The permeate is mixed with the D-allulose-rich composition provided in step a); and

This mixture is subjected to the concentration step b) to provide the mother solution to crystallize;

At least part of the mother liquor and / or the retentate is purged.

According to a second embodiment, the method comprises:

a) a step of providing a composition rich in D-allulose;

b) a concentration step for forming the mother solution to crystallize;

characterized in that

At least one recycling step consists of a step of recycling at least a portion of the mother liquors;

These recycled mother liquors are mixed with the composition rich in D-allulose provided in step a);

The nanofiltration step is performed on this mixture to provide a permeate and a retentate;

This permeate is subjected to the concentration step b) to provide the mother solution to crystallize; and

At least part of the mother liquor is purged.

According to a third embodiment, the method comprises:

a) a step of providing a composition comprising D-allulose and D-fructose; b) a chromatography step to provide a composition rich in D-allulose and a raffinate consisting of a composition rich in D-fructose;

c) a step of concentrating the composition rich in D-allulose to form the mother solution to be crystallized;

characterized in that

At least one recycling step consists of a step of recycling at least a portion of the mother liquors; The nanofiltration step is carried out on these recycled mother liquors to form a permeate and a retentate;

The permeate is mixed with the composition provided in step a);

This mixture is subjected to the chromatography step b); and

At least part of the mother liquor is purged.

According to a fourth embodiment, the method comprises:

a) a step of providing a composition comprising D-allulose and D-fructose; b) a chromatography step to provide a composition rich in D-allulose and a composition rich in D-fructose;

c) a concentration step for forming the mother solution to crystallize;

characterized in that

These recycled mother liquors are mixed with the composition provided in step a);

This permeate is subjected to the chromatography step b); and

At least part of the mother liquor is purged.

According to a fifth embodiment, the method comprises:

c) a concentration step for forming the mother solution to crystallize;

characterized in that

These recycled mother liquors are mixed with the composition provided in step a); · The chromatography step b) is performed on this mixture;

The nanofiltration step is performed on the composition rich in D-allulose resulting from this chromatography step b), to provide a permeate and a retentate;

This permeate is subjected to the concentration step c); and

At least part of the mother liquor is purged.

According to a sixth embodiment, the method comprises:

a) a step of providing a composition comprising D-fructose;

b) an epimerization step to form a composition comprising D-fructose and D-allulose;

c) a chromatography step of this composition to provide a composition rich in D-allulose and a raffinate consisting of a composition rich in D-fructose;

d) a step of concentrating the composition rich in D-allulose to form the mother solution to crystallize;

characterized in that

At least one recycling step consists of a step of recycling the raffinate;

The nanofiltration step is carried out on this raffinate to provide a permeate and a retentate;

The permeate is mixed with the composition comprising D-fructose of step a);

The epimerization stage b) is carried out on this mixture and;

At least a portion of the raffinate is purged. According to a seventh embodiment, the method comprises:

a) a step of providing a composition comprising D-fructose;

d) a concentration step to form the mother solution to crystallize;

characterized in that

A recycling step consists of a step of recycling the raffinate obtained in step c);

A first nanofiltration step is performed on this raffinate to provide a first permeate and a first retentate;

The first permeate is mixed with the composition comprising D-fructose of step a);

The epimerization stage b) is carried out on this mixture;

A recycling step consists of a step of recycling at least a portion of the mother liquors;

A second nanofiltration step is performed on these recycled mother liquors to form a second permeate and a second retentate;

The second permeate is mixed with the D-allulose-rich composition provided in step c);

This mixture is subjected to the concentration step d) to provide the stock solution to crystallize and;

At least a portion of the raffinate and / or mother liquors are purged.

According to an eighth embodiment, the method comprises:

a) a step of providing a composition comprising D-fructose;

d) a concentration step to form the mother solution to crystallize; characterized in that

The epimerization stage b) is carried out on this mixture;

These recycled mother liquors are mixed with the composition rich in D-allulose supplied in step c);

A second nanofiltration step is performed on this mixture to provide a second permeate and a second retentate;

This second permeate is subjected to the concentration step d) to provide the mother solution to crystallize and;

At least a portion of the raffinate and / or mother liquors are purged.

According to a ninth embodiment, the method comprises:

a) a step of providing a composition comprising D-fructose;

c) a chromatography step to provide a composition rich in D-allulose and a raffinate consisting of a composition rich in D-fructose;

d) a step of concentrating the composition rich in D-allulose to form the mother solution to crystallize; characterized in that

A first nanofiltration step is performed on this raffinate to provide a first permeate and a first retentate; The first permeate is mixed with the composition comprising D-fructose of step a);

The epimerization stage b) is carried out on this mixture;

The second permeate is mixed with the composition formed in step b);

This mixture is subjected to step c) of chromatography; and

At least a portion of the raffinate and / or mother liquors are purged.

According to a tenth embodiment, the method comprises:

a) a step of providing a composition comprising D-fructose;

characterized in that

The epimerization stage b) is carried out on this mixture;

These recycled mother liquors are mixed with the composition formed in step b);

This second permeate is subjected to the chromatography step c); and At least a portion of the raffinate and / or mother liquors are purged.

According to an eleventh embodiment, the method comprises:

a) a step of providing a composition comprising D-fructose;

characterized in that

The epimerization stage b) is carried out on this mixture;

These recycled mother liquors are mixed with the composition formed in step b);

The chromatography step c) is carried out on this mixture;

A second nanofiltration step is performed on the composition rich in D-allulose resulting from this chromatography step b), to provide a second permeate and a second retentate;

This second permeate is subjected to the concentration step c); and

At least a portion of the raffinate and / or mother liquors are purged.

Without limitation, the invention will now be detailed to illustrate its interest in the examples below. Examples

Analytical methods

Chromatography in gas phase

The gas chromatograph used is of the Varian 3800 type and is equipped with:

- A split-splitless injector (with or without dividers);

A flame ionization detector (FID);

A computer system for processing the detector signal;

An automatic sampler (type 8400).

The different amounts are determined by gas chromatography in the form of trimethylsilylated methoxim derivatives, and then quantified by the internal calibration method.

Determination of D-allulose, D-fructose and glucose contents

The response coefficients applied are 1.25 for D-allulose and D-fructose and 1.23 for glucose. The other monosaccharides were not detected.

Sample preparation

In a tare box, weigh 100 to 300 mg of the test sample + 10 ml internal standard solution consisting of methyl α-D-glucopyranoside at 0.3 mg / ml in pyridine. In a 2 ml cup, take 0.5 ml from the tare box and evaporate to dryness under a stream of nitrogen. Add 20 mg of methoxylamine hydrochloride and 1 ml of pyridine. Stopper and leave in the Reacti-therm ® incubation system at 70 ° C for 40 min. Add 0.5 ml of N, O bis (trimethylsilyl) trifluoroacetamide (BSTFA). Heat for 30 minutes at 70 ^< C.

Chromatographic conditions

Column: capillary DB1 40 meters, internal diameter 0.18 mm, 0.4μηη film thickness, made of 100% dimethylpolysiloxane, apolar (J & W Scientific ref .: 121-1043)

Column temperature: 100 ^ programming to 260 ° C at 3 ° C / m \ n, then up to 300 ^<C to 15 ^<C / min, hold 5 min at 300 ^<C.

Injector temperature: 300 ° C

Detector temperature: 300 ° C (Range 10 ² )

Pressure: 40 psi (constant flow)

Vector gas: Helium Injection mode: Split (split flow: 100 ml / min)

Injected volume: 1, ΟμΙ

D-allulose, D-fructose and glucose were detected in that order. D-allulose, which was unknown, has a retention time in these conditions of between 39.5 and 40 minutes.

Determination of dimers of D-allulose and glucose-glucose dimer

The response coefficients applied are 1.15 for D-allulose dimers and maltose, and 1.08 for isomaltose. The other glucose dimers were not detected. Sample preparation:

In a tare box, weigh 100 to 300 mg of the test sample + 10 ml internal standard solution consisting of Phenyl beta-D-glucopyranoside at 0.3 mg / ml in pyridine.

In a 2 ml cup, take 0.5 ml from the tare box and evaporate to dryness under a stream of nitrogen.

Take up with 0.5 ml of the hydroxylamine hydrochloride solution at 40 g / l in pyridine, stop, stir and leave for 40 min at 70 ° C.

Add 0.4 ml of BSTFA and 0.1 ml of N-trimethylsilylimidazole (TSIM). Heat for 30 minutes at 70 ^<C. Chromatographic conditions

Column: capillary DB1 30 meters, internal diameter 0.32 mm, film thickness 0.25μηη (J & W Scientific ref .: 123-1032)

Column temperature: 200 ° C programming up to 280 ° C at 5 ° C / min (maintain 6 min), then up to 320 ^ at 5 ° C / min, maintain 5 min at 320 ° C ^.

Injector temperature: 300 ° C

Detector temperature: 300 ° C (Range 10 ² )

Pressure: 14 psi (constant flow)

Vector gas: Helium

Injection mode: Split (split flow: 80 ml / min)

Injected volume: 1, 2μΙ Expression of results:

The content of the various constituents is expressed in g per 100 g of crude product and is given by the following equation: Si Pe 100

% constituting i = x x

Se P Ki

With:

If = surface of the constituent peak (s) i

Se = area of the internal standard peak

Pe = Weight of internal standard introduced into the beaker (in mg)

P = weight of sample weighed (in mg)

Ki = coefficient of response of the constituent i If the percentage obtained (expressed here in gross) exceeds 20% for one of the constituents, the sample is diluted and the GC analysis recommenced in order to obtain a mass quantity of less than 20%.

The mass quantities expressed in crude are then expressed in dry form, dividing for the dry matter of the tested sample.

The mass quantities of D-allulose, D-fructose and glucose are easily determined, none of the characteristic peaks being co-eluted.

The peak of maltose and D-allulose dimers can be co-eluted. It should be noted, however, that in the crystals of the invention and described in the examples below, maltose is never present.

If the characteristic peaks of maltose are not detected, the surface area of D-allulose dimers D is determined by integration of unknown peaks, between 10 and 17 minutes. If the characteristic peaks of the maltose are detected (which may be the case in the syrups of the invention), the amounts of maltose are determined and this amount is subtracted from the total amount of the dimers.

To determine the total amount of glucose-glucose dimer, the following protocol is carried out on a sample: • Hydrolysis hydrochloride

In a 15 ml Teflon screw cap, weigh approximately 50-500 mg of sample (adjust the weighing according to the expected sugar content), add 2 ml to the double-streaked pipette of the d solution. internal standard (galactitol 5 mg / ml in osmosis water), add 3 ml of water and 5 ml of the 4N HCl solution.

Close tightly and shake for 1 minute on the vortex mixer. Place the tube in a thermostatically controlled dry bath at 100 ° C for 1 hour, vortexing occasionally.

• Demineralization and concentration

After cooling in a 50 ml beaker, remove all the hydrolysis. Add 6 to 8 g of a 50/50 mixture of anionic resin AG4 X4 and AG50 W 8. Leave under magnetic stirring for 5 minutes. Filter on paper. Recover the juice and repeat the demineralization step until a pH close to the water.

• Sample preparation

In a tare box, weigh 100 to 300 mg of the test sample + 10 ml internal standard solution consisting of methyl α-D-glucopyranoside at 0.3 mg / ml in pyridine. In a 2 ml cup, take 0.5 ml from the tare box and evaporate to dryness under a stream of nitrogen. Add 20 mg of methoxylamine hydrochloride and 1 ml of pyridine. Stopper and let Reacti-therm® at 70 ^< Ό for 40 minutes. Add 0.5 ml of BSTFA. Heat 30 min to 70 ^< €.

The amount of total glucose of the solution (which comprises the initial glucose called "free" and the glucose resulting from the hydrolysis and in particular related to the presence of maltose and isomaltose) is determined by GPC analysis of glucose. It is easy to deduce the amount of maltose and, by difference with the total amount of dimers attributed to the peaks between 10 and 17 minutes, the amount of D-allulose dimers. sizer

The values of average volume size D 4.3 as well as ratio of Feret min / Feret max diameters of the crystals are determined on a QAPROTEC type QICPIC RODOS granulometer, equipped with its powder dispersion module (dry process), following the technical manual and the manufacturer's specifications. Realization of continuous industrial processes for the manufacture of D-allulose crystals

Example 1

Example 1 consists of a method of continuous production of D-allulose crystals. The steps of the process used are detailed in Figure 3. The composition and flow rate of fluxes after stabilization in the process are described in Tables 1a and 1b.

Step 1 :

13.1 tonnes of a mixture consisting of 26% of a Fructamyl D-fructose syrup (Tereos) comprising 95% of D-fructose containing 50% of dry matter (13%) are introduced into a stirred batch reactor of useful 12m ^3. MS) (Fluxl), and 74% Flux 16 reduced to 50% MS. The whole (Stream 1 ') is maintained at 55 ° C. A lyophilizate of the strain Bacillus subtilis host of the enzyme D-Psicose 3 Epimerase detailed in the patent WO2015032761 is introduced into the vat in an amount sufficient to have 2.5 ^* 10 ⁷ activity units in the reactor. Five reactors are used sequentially to provide a syrup consisting essentially of fructose and allulose (Flux 2) continuously at a rate of 1.3 t / h. The conditions of the reaction are as follows:

• Temperature: 55 ° C

• pH = 7

• Response time 48h

At the end of the reaction, the Flux 2 is obtained comprises a richness in D-allulose approximately equal to 25% and a richness in D-fructose approximately equal to 75%.

2nd step :

Flux 2 passes through a microfiltration membrane during a batch operation. A Flux 3 free of cellular debris and a microfiltration retentate (Stream 17) comprising the debris from the Bacillus subtilis freeze-dried which is purged from the circuit is obtained. The microfiltration parameters are as follows:

• Transmembrane pressure: 0-3 bar

• Pore size: 0.1 μηη

• Temperature: 50 ° C

• Average flow rate: 15 l / h / m ²

· Membrane: Sepro PS35

• Concentration Volume Factor: 33 Table 1a: Flow Rates and Flow Composition of Steps 1 to 5 of Example 1

Step / Flow Flux Characteristics

Step 1 Flow 1 Flow 16 Flow V

Mass flow (kg / h) 360 1005 1365

Dry matter (%) 50 50 50

Fructose Wealth (%) 94.5 75.5 80.5

Dextrose Wealth (%) 2 6.6 5.4

Wealth Allulose (%) 1 2, 1 1, 7

Di-Allulose Wealth (%) 1 10.9 8.3

Wealth Other (%) 1, 5 4.9 4, 1

Step 2 / Step 3 Flux2 / 3/4 Stream 17 -

Mass flow (kg / h) 1324 41 -

Dry matter (%) 50 50 -

Step 4 Flow 4 'Flow 14 Flow 5

Mass flow (kg / h) 1673 2061 2993

Dry matter (%) 50,2 26,2 10

Fructose Wealth (%) 49.6 75.5 2.8

Dextrose Richness (%) 4.5 6.6 0.6

Wealth Allulose (%) 33.4 2, 1 90, 1

Di-Allulose Wealth (%) 8.3 10.9 3.5

Wealth Other (%) 4.2 4.9 3

Step 5 Flow 5 Flow 6 Flux12

Mass flow (kg / h) 2993 2797 196

Dry matter (%) 10 8.7 29

Fructose Wealth (%) 2.8 2.7 3

Dextrose Richness (%) 0.6 0.6 0.7

Wealth Allulose (%) 90.1 94.4 71, 7

Di-Allulose Wealth (%) 3.5 0.4 16.6

Wealth Other (%) 3 1, 9 8 Table 1b: Flow Rates and Flow Composition of Steps 6 to 9 of Example 1

Step / Feature Flow

Step 6 Flow 6 Flow 7 -

Mass flow (kg / h) 2797 279 -

Dry matter (%) 8.7 87 -

Fructose Wealth (%) 2.7 2.7 -

Dextrose Richness (%) 0.6 0.6 -

Wealth Allulose (%) 94.4 93.7 -

Di-Allulose Wealth (%) 0.4 1, 1 -

Wealth Other (%) 1, 9 1, 9 -

Step 7a / 7b Flux7 / 8/9 -

Mass flow (kg / h) 279 - -

Dry matter (%) 87 - -

Step 8 Flux 9 Fluxl O Flux 13

Mass flow (kg / h) 279 126 152

Dry matter (%) 87 97 76,5

Fructose Wealth (%) 2.7 0.1 5.4

Dextrose Richness (%) 0.6 0 1, 2

Wealth Allulose (%) 93.7 99.7 87.5

Di-Allulose Wealth (%) 1, 1 0.2 2.2

Wealth Other (%) 1, 9 0 3.7

Step 9 Flow 10 Flow1 1 -

Mass flow (kg / h) 126 122 -

Dry matter (%) 97 99,8 - Step 3:

Flux 3 is demineralized by passage over a strong Dowex 88 cationic resin and then a Dowex 66 weak anionic resin at an average flow rate of 2BV / h. The cylinders are maintained at a temperature of 45 ^q C and the resistivity of Flux 4 at the end of the demineralization remains greater than 100 kΩ crrv ¹ at the output (stream 4). In the opposite case, the regeneration of the resins is carried out.

Step 4:

Flux 4 is mixed with Flux 12 (nanofiltration retentate) and Flux 13 (crystallization mother liquors) to form a Flux 4 'which feeds simulated mobile bed continuous chromatography (SMB) (SCC ARI® equipped with 8 columns) of the circuit. The average feed rate is 1673kg / h at 50% DM.

The parameters of the chromatography are defined as follows:

• Volume / column: 2m ³

• Resin: Dowex Monosphere 99Ca / 320

· Temperature: 60 ° C

• Water flow / Flow 4 '(vol./vol.): 2,4

• Load (feed rate / resin volume): 0.09 h ^-1

Two fractions are extracted: the raffinate of the SCC (Flux 14), the fraction rich in D-allulose (Stream 5) which leaves towards the step 5. 7% of the Flux 14 is purged (Stream 15) in order to remove the allulose dimers while the remainder (stream 16) goes back to stage 1 after having been brought back to a dry matter of 50% by means of an evaporator.

Step 5:

Flux 5 is processed on a nanofiltration installation in batch mode. The settings are as follows:

· Trans-membrane pressure: 30 bar

• Temperature: 20 ° C

• Membrane: GE Duracon NF1 8040C35

• Concentration Volume Factor (VCF): 16

The allulose dimers are concentrated in the retentate (Flux 12) and this retentate is recycled and mixed with Flux 4 while the permeate (Stream 6) is recovered. Figure 6 gives details of permeation of syrups as a function of FCV. Step 6:

Flux 6 passes through a two-stage evaporator whose internal pressure is 50 mbar. At the outlet of the first stage, the Flux is at a temperature of 38 ° C. and has a solids content of 35%. At the outlet of the second stage, the Flux reaches a temperature of 48 ° C and has 87% of dry matter. The stock solution of D-allulose (Stream 7) is obtained at the end of this stage.

Step 7a:

The stock solution thus formed (Stream 7) is introduced immediately after being heated to 68 ° C by an exchanger, in a vacuum crystallizer-evaporator vacuum of 3m ³ useful, within which the pressure is maintained at 35mbars.

The principle of operation of the vacuum adiabatic evaporator crystallizer used here is detailed in Figure 4:

• Flux 7a is composed of D-allulose syrup supersaturated at 35 ° C and the finest particles of D-allulose. It is mixed with Flux 7 in a ratio such that the mixture is just below the solubility limit of the mixture (84% dry matter and 46 ^q C) (Stream 7b). The fine particles are thus melted down.

• The mass-cooked is withdrawn from the adiabatic crystallizer-evaporator at a temperature of 35 ° C, at the same speed as the mixture, so as to maintain the constant level in the adiabatic crystallizer-evaporator. This mass-cooked recovered is separated into two streams: Flux 7d and Flux 8. Flux 7d is driven with Flux 7b to form a Flux 7c comprising the stock solution of D-allulose and primers for crystallization. The mixing ratio is made so as to find again beyond the solubility (85.5% dry matter and 42, 7 ^q C) so that the crystals can continue their magnifications.

Flux 7c is thus introduced into the crystallizer-evaporator adiabatic vacuum to prolong the crystallization and form the mass-cooked. The condensed water during this stage is reinjected continuously along the walls at the top of the crystallizer.

The different Fluxes during the evapo-cooling stage in the vacuum crystallizer-adiabatic evaporator is reported in Table 2. Table 2: Characteristics of the Different Fluxes in the Vacuum Adiabatic Crystallizer-Evaporator

Step 7b:

The bunker is withdrawn at the top of the vertical crystallizer with a working volume of 8 m ³ and equipped with an agitator and five cooling plies. The massecuite is brought from 35 to 20 ° C in 40h, a cooling ramp of about 0.4 ° C / h. The diagram of the crystallizer is shown in Figure 5. The temperature of the cooling water in the layers is as follows:

1. 34 ^< € for entry, 32 ^< € for exit

2. 31 ° C input, 29 ^< € output

3. 28 ° C inlet, 26 ° C outlet

4. 25 ° C input, 22 ^< € output

5. 21 ° C inlet, 20 ^< C outlet

Step 8:

At the bottom of the crystallizer, the crystal suspension (Flux 9) is recovered and then centrifuged on a Rousselet Robatel SC 100KSA wringer. The crystal suspension is systematically centrifugable, which means that the process is very stable over time. The mother liquors (Flux 13) are recycled and mixed with Fluxes 4 and 12. The wet crystals of D-allulose (Flux 10) are recovered. A first water and then a final clearing with ethanol of the order of 0.5% w / w is performed to improve the separation. The clear crystals comprise 3% water.

Step 9:

The wet crystals pass through a rotary drier and dried crystals are obtained which comprise 0.4% water. Final cooling in a fluidized bed lowers the temperature of the crystals from 60 to 25%. The final crystals are recovered (Flux 1 1) and then packaged. The overall yield of crystals of D-allulose, which is the ratio expressed in dry mass of the mass of D-allulose crystals obtained on the mass of D-fructose introduced, is 72%.

Example 2

Example 2 is identical to Example 1 except that no recycling is carried out. Flux 7 comprises 0.7% dimers of D-allulose. The suspension of crystals of Flux 9 is always centrifugable over time. Although the overall yield of crystals is only 12%, the method has the advantage of being stable, unlike the methods of the comparative examples, not using the nanofiltration step, which will be presented hereinafter.

Comparative Example 1

Comparative Example 1 is identical to Example 1 except that:

• no nanofiltration step is performed,

• no recycling stage of the mother liquor is carried out,

· The recycling of raffinate (Flux 14) is recycled in its entirety to be mixed with Flux 1 of D-fructose syrup,

The crystallization step is carried out as follows: the stock-formed solution (Flux 7) is introduced sequentially into three vertical crystallizers with a working volume of 8 m ³ identical to that used for the crystallization step 7b of Example 1. the cooling gradient is Ο, ββ'Ό / ϊι ^q up to 20 C. in each crystallizer was charged with a primer of D-allulose of D4,3 equal to about 60μηη in mass quantities of 0.1%, this amount being expressed relative to the dry weight of D-allulose introduced into the crystallizer.

The production circuit used (i.e the different steps of the method used) is that corresponding to Figure 1.

Flux 7 comprises 1.9% d-allulose dimers. A Flux 9 is recovered which is led to step 8. This Flux 9 is a mass-cooked which is not always centrifugable. After one week, the Flux 7 comprises 2.2% D-allulose dimers and the mass-cooked Flux 9 even becomes systematically non-centrifugable (crystals too small).

Comparative Example 2 Comparative Example 2 is identical to Comparative Example 1 except that the mother liquors are completely recycled (Stream 13) to be mixed with the composition rich in D-allulose resulting from the chromatography step (Stream 5) and that the raffinate (Flux 14) is not recycled and is purged from the circuit.

The production circuit used is that corresponding to Figure 2.

Flux 7 comprises 1.9% d-allulose dimers. A Flux 9 is recovered which is led to step 8. This Flux 9 is a mass-cooked which is not always centrifugable. As soon as the mother liquors are recycled, Flux 7 comprises 2.4% of D-allulose dimers and Flux 9's mass-cooked even becomes systematically non-centrifugable (too small crystals).

Comparative Example 3

Comparative Example 3 is identical to Comparative Example 1 except that the raffinate is not recycled.

The production circuit used is that corresponding to Figure 1.

Flux 7 comprises 1.9% d-allulose dimers. A Flux 9 is recovered which is led to step 8. This Flux 9 is a mass-cooked which is not always centrifugable. When centrifugable, the mother liquors separate from the allulose crystals that can be recovered. But sometimes Flux 9 consists of a mass of small indissociable crystals, synonymous with a spontaneous nucleation in the crystallizer. In this case, it is necessary to drain the flow of the circuit. This makes the process unusable industrially.

The summary of the results obtained for these processes are reported in Table 3. The overall reported yield is an average over one week of use.

The characteristics of the crystals obtained for Examples 1, 2 and Comparative Example 3, as well as the crystals of D-allulose sold by CJ Cheiljedang Food Ingredient, are reported in Table 4.

Table 3: Comparison of the different circuits tested

The process of the invention makes it possible to obtain stable crystallization over time, which is demonstrated in the industrial process exemplified above (Examples 1 and 2). It also makes it possible to carry out very large recycling operations and thus to increase the overall yield of D-allulose crystals (see Example 2). By carrying out recycles without ensuring that the D-allulose dimers are separated by the nanofiltration step, the illustrative Comparative Examples 1 and 2 above demonstrated that the industrial crystallization process should be stopped as the mass-cooked product becomes systematically non-centrifugable (small crystals).

Table 4: Characteristic of the crystals obtained

FIG. 14, which shows, for the crystals of Example 2 and the crystals marketed by CJ of D-allulose, the ratio of Feret min / Feret max diameters as a function of the particle size in volume D4,3, demonstrates that is for populations of large size, greater than or equal to 200Mm (for example in the range of 200 to 400 Mm), that clear differences in appearance are observed between the crystals according to the invention and the comparative crystals. Thus, in this range of from 200 to 400 μm, the Feret min / Feret max ratios are, for the comparative crystals, always less than 0.55 whereas the crystals according to the invention have a ratio of at least 0.63. . This difference is entirely in agreement with the optical microscopy images of FIGS. 11 and 12, which visually demonstrate that the crystals according to the invention have a much more stocky appearance than the comparative crystals. With regard to the crystals of CJ of Figure 13 (optical microscopy images), it is noted that they are crystals in the form of needles, not individualized.

Although Comparative Example 3 is not strictly identical to the teaching of the document WO 201 11 19004 A2 with regard to the concentration step (in particular in that the Applicant has managed to perform more optimally the concentration step so as to further reduce the amount of D-allulose dimers formed), the The crystals obtained use a process of the same type as that used to manufacture the crystals described in Example 6 of WO 201 11 19004 A2 (especially with regard to the crystallization is carried out exclusively by controlled cooling in water). This comparative test 3, producing crystals comprising 0.7% D-allulose dimers, thus clearly demonstrates that the document WO 201 11 19004 A2 does not make it possible to form the crystals of the invention.

Use of the crystals of the invention in different applications

The crystals of Example 2 were used in the manufacture of the following products.

Manufacture of meal replacement beverages

The goal is to create a meal replacement powder drink with few calories. This powdered beverage must be able to have a good flow and form few lumps when it is formulated.

Formula

After weighing, the ingredients are vigorously mixed in a dry blender. The beverage is then easily reconstituted by adding 210 g of water to 30 g of the formula, without forming lumps.

The formula using the crystals of the invention exhibit a flow behavior quite similar to the formula comprising sucrose, while having much fewer calories. Yellow cake making

The goal is to provide a yellow cake with a satisfactory texture and appearance with a caloric content of 25%. Formula

Method:

1. Mix the flour, salt, Nutriose® and yeast;

2. Cream butter with sucrose or allulose;

3. Add the egg yolk and vanilla to the cream then add the milk to form a creamy mixture;

4. Add the flour mixture to the cream mixture and mix in a slow blender (1 minute) and then stir until mixture is well mixed;

5. Pour 600 g of the dough into a 9-inch greased circular pan;

6. Bake at 180 ° C for 20 minutes. The objective is achieved: the cake using the crystals of the invention has a very pleasant texture in the mouth (we speak of "crumb texture") and the shape of the cake is maintained after cooking. Manufacture of chocolate cookies

The following formulas have been realized:

Ingredients Reference Allulose Allulose + Nutriose®

Wheat flour 25 25 23

Baking soda 0.14 0.14 0.14

Salt 0.17 0.17 0.17

Melted butter 14,16 14,16 14,16

Nutriose® FB06 0 0 2

Allulose 0 29.17 29.17

Brown sugar 20.35 0 0

Sugar powder 8,82 0 0

Vanilla 1, 14 1, 14 1, 14

Eggs 7 7 7

Chocolate chips 23,22 23,22 23,22

Total 100 100 100

Method:

1. Mix the dry ingredients together;

2. Cream butter with sugars or allulose;

3. Add the eggs and vanilla to the creamy mixture;

5. Add the chocolate chips and mix;

6. Weigh portions of 30 g and cook at 160 ^ for 8 minutes.

The allulose cookie dough (column 2) spreads less than the sugar-based dough (column 1). However, the pulp of column 3 spreads in the same way as the pulp of column 1.

During cooking, allulose cookies turn brown faster.

It should be noted that cookies have a dome shape. The height of the cookie according to the invention is less inflated and it does not collapse after cooking, unlike the cookie-based sugars, which allows it to keep a better appearance.

Allulose cookies have a good taste, although less sweet. The texture of the cookies according to the invention is soft and wetter than sugar-based cookies.

The activity of the water (w a) and the humidity (M) of the cookies are measured over time:

Allulose cookies have better moisture stability. Production of oatmeal cookies

Formulas:

^* Inclusions include 50.0 grams of pecan nuts, 20.0 grams of cranberries and 18.6 grams of blueberries.

Method:

1. Mix the flour, Nutriose®, baking soda, yeast and salt;

2. Cream butter with sugars or allulose;

3. Add the eggs and vanilla to the creamy mixture;

5. Add the oatmeal and mix; 6. Add the inclusions and mix;

7. Weigh portions of 30 g and cook ^\ 60 ° C for 10 minutes.

The cookies obtained using allulose instead of sucrose, are slightly browner and have a crispy texture after cooking.

Bubble gum making

A bubble gum was made with the recipe below:

Bubble gum has a very satisfactory appearance, similar to the bubblegum trade.

Claims

1. A process for producing D-allulose crystals comprising:

A step of providing a composition rich in D-allulose,

2. Method according to claim 1 characterized in that the membrane used for nanofiltration has a cutoff threshold of less than 300 Da, preferably ranging from 150 to 250 Da.

3. Method according to one of the preceding claims characterized in that the stock solution obtained comprises in dry mass:

From 80 to 99% of D-allulose, preferably from 85 to 98%;

From 0 to 20% of D-fructose, preferably from 0.5 to 15%;

0 to 10% glucose, preferably 0 to 5%;

4. Method according to one of the preceding claims characterized in that the volume concentration factor of the nanofiltration is from 5 to 20.

5. Method according to one of the preceding claims characterized in that the crystallization step comprises:

i. an adiabatic evapo-cooling stage, carried out in an adiabatic evaporator / evaporator under vacuum to form a massecuite,

ii. followed by a crystallization stage by cooling said massecuite to form crystals.

6. Method according to claim 5 characterized in that the temperature during the adiabatic evapo-cooling stage ranges from 30 to 40 ° C, preferably from 33 to 37 ^q C, for example about 35 ° C.

7. Method according to one of the preceding claims characterized in that it is continuous.

8. Method according to one of the preceding claims characterized in that it comprises at least one recycling step.

9. Method according to one of the preceding claims characterized in that it comprises a step of recycling at least a portion of the mother liquors.

10. Method according to one of the preceding claims characterized in that the step of providing the stock solution of D-allulose comprises:

A step of providing a composition rich in D-allulose;

A nanofiltration permeate recovery step;

1. Process according to claim 10, characterized in that it comprises a step of recycling at least a part of the retentate.

12. Method according to one of claims 10 or 1 1 characterized in that the step of providing the composition rich in D-allulose comprises:

A step of providing a composition comprising D-fructose;

An epimerization step to form a composition comprising D-fructose and D-allulose;

A chromatography step to provide a composition rich in D-allulose and a composition rich in D-fructose.

13. The method of claim 12 characterized in that it comprises a step of recycling at least a portion of the composition rich in D-fructose.

14. The method of claim 13 characterized in that the recycling rate of the composition rich in D-fructose ranges from 50 to 95%.

15. D-Allulose crystals comprising a mass content of D-allulose dimer, determined by gas chromatography (GC), of less than 0.50%.

16. D-allulose crystals according to claim 15, characterized in that they comprise a mass content of D-allulose dimer ranging from 0.01 to 0.48%, preferably ranging from 0.02 to 0.45%, for example ranging from 0.03 to 0.40%, especially from 0.04 to

0.30%.

17. Crystals of D-allulose according to one of claims 15 and 16 characterized in that they have a mean volume size D4,3 greater than 200 μηη, preferably from 210 to 800μηη, preferably from 220 to 350 Mm.

18. D-allulose crystals according to one of claims 15 to 17 characterized in that they have, for a given particle size D4,3 volume and selected in the range from 200 to 400μηη, a ratio Feret min / Feret max greater than 0.60, advantageously ranging from 0.62 to 0.90, for example from 0.63 to 0.80.

19. Crystals of D-allulose according to claim 17 characterized in that they have this ratio Feret min / Feret max on all volume particle sizes D4,3 in the range from 200 to 400μηη.

20. Use of a nanofiltration unit in a D-allulose crystal production circuit to improve the overall yield of D-allulose crystals.